Diaphragm.



D. M. BUSS.

DIAPHRAGM.

APPLICATION FILED OCT. 4, 1916.

1, 57?,538. Pqtent'edSept. 3,1918.

INVENTOR.

ATTORNEYS. 7

UNITED STATES PATENT OFFICE.

DONALD M- BLISS, or waste ORANGE, NEW JERSEY.

DIAPHRAGM.

Specification of Letters Patent? Patented Sept. 3, 1918.

- Application filed October 4, 1916. Serial No. 123,625.

' To all whom iii may concern.-

Be it. known that I, Doxann M. Brass, a citizen of the Dominion of Canada, residmg at \Vest' Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Diaphragms, of which the following is a speci fication.

My invention relates to phonograph or talking machine reproducers and especially to improved diaphragms and coacting parts. In the construction of sound-boxes for phonographs the principal difficulty which has been encountered has been the fact that the mass and low resilience of the diaphragm has prevented the same from following the stylus lever accurately. For the same reasons the usual diaphragm absorbs a large percentage of the higher frequencies of sound vibration so that the more delicate over-tones are not Well reproduced and the reproduction of articulation is imperfect.

In results heretofore attained the diaphragm has either been adapted to reproduce most of the tones encountered with a slighting of the higher frequencies, as stated above, or when the diaphragm has been made smaller in diameter and lighter in weight the production of thehigher frequencies has been improved but'results in other respects have been imperfect. Considering'many of the materials now largely used for making diaphragms such as mica, celluloid, wood, fiber, thin metal and others,

if a diaphragm made of such materials is constructed of a sufficiently large diameter to reproduce a tone of varying pitch in proper balance, its inertia will be so great that the higher frequencies or soprano tones will be reduced in volume and quality, ar.-'

ticulation will be imperfect and the diaphragm will not follow the movement of the stylus lever accurately. On the other hand, as stated, if such a diaphragm is made smaller in diameter and lighter in Weight; it will follow the undulations of the record morefaithfully but the proper balance be tween the different voices, in the case of a musical record, will be lost and the result will be to give a reproductionof a thin nasal quality.

I have found that if a diaphragm be constructed in such a way that its center portion is made of-mater1al 1n a conditlon of diaphragm is made of a relatively light and thick material having. a large opening through its center. A small thin diaphragm of relatively dense material and higher resilience'is secured on the outer face of the large diaphragm in alinement with and overlapping'this opening. YVith this con?- struction soprano or other tones of high frequency willvibrate the small central diaphragm practically without any dissipation" in'or through the heavy diaphragm of dif ferent density to which the central diaphragm is secured. Vibrations of deeper tone and greater energy, however, will vibrate the diaphragm as a whole.

The objects of my invention reside in im' proved construction for producing effects and en'ibodying the principle referred to above. Other objects reside in the combinations of parts and details of constructionas will appeai more fully hereinafter.

In order that a clearer understanding of my invention may be had, attention is hereby directed to the following drawings forming part of my.application and illustrating certain embodiments of my invention. In: the drawings, Figure 1 represents a central"- vertical section through a sound boX embodying one form of my invention, Fig. 2

is'a bottom plan view of the same and Fig. 3 is a central vertical section showing a modified form of my invention.

Referring to Figs. Land 2 of the drawings, a sound box 1- is provided with a dia phragm the chief member or portion of which is shown at 2 comprising a disk having a relatively large central opening 3 therethrough. The annular disk 2 may be formed of cork, wood, fiberor other suitable materials, preferably lightin character, the member 2 also being of considerable thickness relatively to the other member of the I diaphragm. This other member 4 comprises a small thin disk of relatively dense material and high resilience in comparison with the member 2. Suitable materials for the central member I are mica, glass, metal, and compressed fiber or cork. Member 4 is secured to the outer face of member 2 about the edge of the opening 3 which latter open ing. it will be noted. forms a sound chamber for the diaphragm l and serves to direct the vibrations produced by member I directly into the neck 5 of the reproducer, to which may be secured the amplifying connection.

The stylus lever 6 carrying stylus 7 may be attached directly t9 the center of the small diaphragm 4 in the usual manner. The diaphragm 2 may be'mounted in a sound-box of the ordinary type between rigid rings or the like, if desired, or it may be mounted on a. flexible supporting surface in the manner illustrated in the drawings. As is there shown, the member 2 securedupon the member 8 of high tensile strength and elasticity, such for example as silkor other strong fabric or membrane, this'flexible support- 8 being secured under a predetern'iined tension between the clamping ring 9 and the annular portion 10 of the sound-box as by means of screws 11. This arrangement is described and claimed in my application, Serial Number 117,577, filed August 30, 1916. The small diaphragm member 4:, vibrating as it does to tones of higher frequency, will also tend to reproduce the scratching sounds due to the movement of the reproducing stylus over the surface of the sound record reproduced. In order to dampen out these scratching or surface sounds and to' suppress the natural tone of the diaphragm 4:, a disk 12, of felt or other suitableimiterial, may be mounted directly on the diaphragm. This dampening disk is secured at its edges to the under or outer surface of the thick diaphragm member :2 adjacentto the edge of diaphragm member at extending across the latter to bear lightly against it.

An alternative construction is illustrated in Fig. 3 in which the main diaphragm.

ber 3' formed therein is of considerably less depth than the corresponding sound-chamber 3 in the form of my invention first described. This sound-chamber, being of insutficient depth to produce the best results, or the peripheral surface boundingthe same being of insuttieientheight to properly direct the sound vibrations produced by diaphragm member a into the neck 5 of the reproducer, it is advisable to provide additional guiding means for this purpose. Accordingly, an annular flange 13 may be formed on the top member or cap of the sound-box extending into the main S0lllKlFllillllbQl ll of the reproducer in substantial alinement with the neck 5 of the reprmlucer and extending into proximity to the adjacent surface of the diaphragm. It will be seen that this COIlStliICtiOIl providesa soi'md-cliamber for diaphragm member e partly formed by diaphragm member 2 and partly formed by the soundbo.\' itself. A

It will be seen that the constructions described above provide diaphragms which are of sutlicient resilience to respond to the high est frequencies while at the same time the total area is suliicient to bring out the reproduction of musical sounds in proper balance. Also owing to the small mass and high resilience of the auxiliary diaphragm a the latter will follow the record vibrations very closely. The auxiliary sound-chamber or sound-directing means provided in the main diaphragm or in the body of the reproducer to coact with the auxiliary diaphragm, directs the sound from the small diaphragm 4; directly into the tone-arm of the phonograph which is connected to the neck 5, which greatly improves the quality of the music or other matter reproduced and the articulation of the same.

It should be noted that the effect of the disparity between the densities, resiliencies and masses of diaphragm members 4 and 2,

is to cause the small diaphragm member 4 to vibrate practically alonein response to tones of high frequency and small energy such as soprano notes or sibilant sounds and other details of articulation. In the usual d1aphragm formed of a single member the tones of higher frequency vibrate only the central v portion of-the diaphragm but these vibrations are absorbed and reduced in volume by the sin-rounding portions of the diaphragm. In the combined diaphragm described herein, however, the main diaphragm of different density from the auxiliary diaphragm 4 acts practically as an insulating non-vibratory member when the diaphragm member 4 is responding to tones of higher frequency only. That is to say, the small member gt vibrates practically alone in such ases with the resulting improvement in volnme 'and quality of the sounds reproduced as described. a

I will now describe my invention antlwhat I claim and desire to protect by Letters Patent is as follows:

1. In a sound reproducer, a compound diaphragm comprising a relatively thick annular disk of low density, and a small central disk of high density and relative thinness secured to said annular disk, substantially as set forth.

2. In a sound reproducer, a compound diaphragm comprising a relatively thick and light-member having a central opening therethrough and a thin member of high density,

relative to that of the first, secured to a face member being relatively thin and of high Q of saidfirst member to cover the opening density and a stylus lever attached to said therein, substantially as set forth. second member, substantially as set forth.

3. In a sound reproducer, the combination This specification signed and witnessed 5 of a sound-box having a diaphragm member this 2d day of October,'1916.

mounted therein said member having a central opening ther ethrough, and being formed DONALD BLISS' of cellularv material, relatively light and Witnesses: I thick, a second diaphragm member secured DYER SMITH, 10 to the first, to cover said opening, said second I. MCINTOSH. 

